GROWERS have been warned that routine subsoiling can have a detrimental effect on long-term soil structure.

Dick Neale, technical manager for Hutchinsons agronomy firm, said they should ensure any cultivation decisions are based on sound science and identified need – not habit or theory.

He said subsoiling can alleviate short-term drainage issues in the following crop, but should only be used to rectify identified compaction issues.

Used routinely, as normally occurs with deep non- inversion tillage, it disrupts natural structuring and may exacerbate future drainage problems.

Mr Neale said: "Rapid passage of water through soil is not a natural process. Water should percolate through slowly and be stored in and between aggregates until needed.

"Subsoiling allows water to quickly drain away from the surface through the large macro pores and fissures created by the leg, but this often sees fine sand and silt particles washed to the base where they pack tightly to form a sedimentation pan.

"This sedimentation can come back to haunt you in following seasons, usually in drought years when root growth is restricted from passing through this hard layer at depth."

He also questioned the value of subsoiling tramlines if the following crop is to be drilled in the same direction as before, resulting in new tramlines over the same position.

"It’s a waste of time and money and means machinery ends up travelling on what is likely to be the softest part of the field," he said.

Wherever possible he said non-mechanical methods, such as cover cropping, traffic management and improvements to organic matter placement to encourage earthworms, should be employed to maintain soil structure through natural processes, thereby improving long-term structure, drainage and water-holding capacity.

Inspecting soil structure is key to deciding the most appropriate cultivation and cropping strategy for individual fields and Hutchinsons have introduced a new Healthy Soils service.

There is also a timely opportunity for farmers to do their own basic assessments of soil structure prior to cultivating land.

Mr Neale said: "Normally soil is too dry to dig inspection holes at this time of year, but the wet summer means there is enough soil moisture to get a good idea of what structure really looks like and make the right decisions about what management is required."

Kieran Walsh, Hutchinsons agronomist in the Cotswolds, said test digs are invaluable for tailoring autumn cultivations, especially where there are big variations in soil type.

He said: "Simple things like looking at the number of worms, texture and smell of the soil can tell you a lot about what’s going on beneath the surface."

In some situations there may be a genuine need for deeper cultivations, but in other cases shallow tillage, or even no cultivation may be more effective.

He said factors such as weed burden add another layer of complexity and can influence cultivation type.

"Soil is the most precious resource we have on farms and I believe in-depth soil analysis is more vital now than at any time in the past," said Mr Walsh.